Field
Embodiments of the present invention relate to a wavelength conversion inorganic member, and a method for manufacturing the same.
Description of the Related Art
A semiconductor light-emitting element such as a light emitting diode or a semiconductor laser is used for a light emitting device which color or wave-length converts a part of or all of light using a color conversion member (a wave-length conversion member). Thus, the converted emitting-light color (emitting-light wave-length) is output. This light-emitting device has been used for a head light and a projector which require a high output.
An exemplary conventional wavelength (color) conversion material used in such light-emitting device is a color conversion material prepared by dispersing a phosphor in a silicone resin which has relatively high heat resistance and light resistance. However, in recent severe applications corresponding to the higher output and higher load of the light source using a semiconductor light emitting device such as a LED (light emitting diode) or a LD (laser diode), the resin used for the color conversion material has the risk of deterioration.
In view of such situation, LEDs and LDs which are free from the use of a resin and other organic substances have been put in practical use. These LEDs and LDs employ a wavelength (color) conversion ceramic material sintered into a plate prepared by solely using an inorganic phosphor or an inorganic phosphor with a transparent inorganic material for the color conversion material for high output, high lord applications.
In addition, various methods have been proposed as a method for producing a wavelength (color) conversion ceramic material solely of an inorganic material.
For example, there is described that a rare earth garnet phosphor which is an inorganic oxide, and in particular, a YAG (yttrium-aluminum-garnet) phosphor as a durable wavelength (color) conversion material (See JP 2004-146835A). While the production method is not disclosed in detail, the color conversion material is produced by preparing polycrystalline ceramics from a base material, and doping an activator which would be the luminescence center. Patent literature 1 discloses use of this polycrystalline ceramic member which is a color conversion material in combination with a semiconductor light emitting device.
There is described that a glass containing an inorganic phosphor for use as a wavelength (color) conversion material and its production method. Use of a YAG phosphor which is an oxide phosphor is mentioned as an example (See JP 2003-258308A).
There is described that a method for producing a light emitting ceramics for use as a wavelength (color) conversion member (See JP 2006-5367A). In this method, an inorganic phosphor is sintered at a high temperature and high pressure.
There is described that production of an inorganic color conversion glass sheet by preparing a sheet from a phosphor powder and a glass powder, and heating the sheet in a high temperature oven (See JP 2006-37097A). Patent literature 4 also discloses use of a low-melting glass having a melting point of up to 400° C. in producing the inorganic color conversion glass sheet from the phosphor of various compounds.
In addition, there is described that precipitation and development of a YAG phosphor from a melt of alumina and the like as a production method of a ceramic composite for light conversion (See JP 2006-169422A).